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Blinking question mark on OS X Boot? Don’t panic just yet.

February 3, 2010 | Computers

My MacBook Pro has been acting up again lately. Crashes, stalls, and overall wacky goodness. Yesterday I pulled it out of my bag after getting home and although I had put it to sleep, and confirmed that it was asleep before packing it away, it had crashed on the way home.

When I restarted it I was faced with a question mark flashing inside a folder icon. The computer couldn’t find a valid system to boot from.

I was able to see a valid system directory when using the Startup Disk selector on the OS X install DVD. I was able to use the Terminal on the DVD to browse the disk as well. All the data was still there.

I tried everything that I could to get it back but had no success. That is, until I ran across a forum post that I now cannot find again. The person in the post had seemingly run across the solution by luck and I’m very thankful he did.

The problem, as it turns out, was that my Master Boot Record was hosed. This is bad. The computer essentially couldn’t find anything that would tell it about the hard drive, so it didn’t even know where to look for a bootable system.

The solution is rather counter-intuitive. At least to me it is. The instructions below are based on OS X 10.6, but I suspect they’ll work on 10.5 as well.

  1. Boot from the OS X install disk.
  2. Instead of installing OS X, select Disk Utility from the Tools menu.
  3. Select the hard drive that is having the problem in the list on the left.
  4. Now select the Partitions tab in the right side of the panel.
  5. If you have one partition, this part is easy. Simply use the slider in the bottom right corner of the partition diagram to resize the partition, then put it back where it was. If you have multiple partitions take note of the size of the partition you’re resizing so you can get it back to right where it was before.
  6. After putting the partition size back the way you found it click the Apply button. You’ll be asked to confirm the decision and told that its non-destructive. Hopefully in all cases this is true πŸ˜‰

So, basically what we’ve done here is forced disk utility to rewrite the master boot record without actually changing the partition structure of the disk, so the existing partition table will simply be re-written to the master boot record.

This works in 10.6, and should probably work in 10.5 as well since it allowed for live disk resizing to support creating Bootcamp installs.

Good luck!

20 Responses

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  • I just wanted to say thanks. Your solution here worked like a charm to fix my problem and saved me even more frustration! Thanks again! I hope you don’t mind but I posted your solution as an excerpt on my own blog.

    Nathan Skarupa, March 16, 2010 12:11 pm | permalink

  • Glad it worked! And thanks for the link back on your blog.

    Shawn, March 16, 2010 12:36 pm | permalink

  • YOU ARE A CHAMPION!!! It totally worked. Stupid Apple tried to get me to reinstall Snow Leopard but I found this page right before doing so. I owe you a beer my friend.

    Paul, April 28, 2010 12:10 pm | permalink

  • This worked for me! I was running MultiBeast on my MacBook to make changes on my CustoMac’s drive, which was loaded externally. I accidentally set the destination as the MacBook’s drive and the MBR got jacked. Oops. Thanks!

    boontok, August 14, 2010 5:05 pm | permalink

  • THANK YOU SO MUCH! You just saved my ass big time.

    Cory, September 29, 2010 10:48 pm | permalink

  • Hi! don’t have Mac OS X disk, what do?

    newbii, October 13, 2010 9:59 pm | permalink

  • Not quite sure what to recommend here. If you don’t see the OS X disk when in the Disk Utility then you’ve got a larger problem on your hands and probably need to dump the drive, buy a new one, and restore from backup.

    Shawn, October 13, 2010 10:28 pm | permalink

  • My son was screwing around with some boot image tools to change the startup image and hosed the OS… blinking questions mark:

    – disk utility – repair disk didn’t work
    – even a reinstall of the OS didn’t work (i didn’t reformat the drive, just a reinstall from the original disk)

    But but this simple trick fixed it for me ! MBR restored… glory days ! I’d like to come over and kiss you. Where do you live ?

    Thankful, November 28, 2010 3:18 pm | permalink

  • I live in Denver and do accept kisses πŸ˜‰

    Shawn, November 28, 2010 3:53 pm | permalink

  • Your solution saved me a lot of time and stress! Thank you!!!!

    Pimski, February 28, 2011 8:33 am | permalink

  • Years later, you’re still saving people’s butts! Thanks! I had spent hours doing all kinds of stuff…reset nvram, pram, verified and repaired permissions, verified and repaired drive, still got the question mark folder at boot up. Reinstalled Snow leopard…still had the problem. Your solution had me at the login screen in five minutes flat, so THANKS!!

    Matt Austin, April 10, 2012 9:07 pm | permalink

  • My God! None of the Apple resources could solve this issue at all, not to mention so elegantly. Im a guy but willing to kiss you too! πŸ™‚ All the best! K

    Papa K, September 22, 2012 9:44 am | permalink

  • Hi,
    many thanks and the same sentiment as everyone else.
    I checked out all the other options and none worked. This one worked like a charm. I have 3 partitions on the drive which would not boot. All I had to do was move the last partition size down then back to its original place filling the rest of the drive as it did originally.
    Sure enough my little old 2007 mac mini running as good as new.
    I’m sure there is a terminal command which would do the same but who needs all that typing πŸ˜‰
    cheers
    G

    Greg in Hong Kong, October 2, 2012 11:16 pm | permalink

  • I tried this but does not word πŸ™ I am UNABLE to access my ‘Disk Utility’ as it says “Mac OS X cannot be installed on this computer”

    When I did get access to ‘Disk Utility’, my Hardrive was not available… HELLPPP!!

    I’m worried I have a virus on my comp :-((

    Zebdy, October 7, 2012 4:51 pm | permalink

  • It sounds more serious in your case. Like maybe a failed hard drive.

    Shawn, October 8, 2012 7:03 am | permalink

  • …or you could just hold down “alt” key when booting up the computer until a disk icon appears.

    Perhaps not in any situation but most probably it will work!:)

    After you get logged in go to System Preferences from the Apple menu top left corner and choose Startup Disk. Select the default disk and go back to work!:)

    H Book, October 5, 2013 1:27 pm | permalink

  • That is true now, yes.

    This post pre-dates the built in recovery partitions. πŸ˜‰

    Shawn, October 5, 2013 6:34 pm | permalink

  • So I am using a 2008 Mac Pro. I am getting this issue after attempting to install Windows 7 via bootcamp. The disk permissions says its ok as well as the disk repair. It just only boots up if I hold the alt key. I have reinstalled mountain lion. I tried the steps you provided below but it is still not working. Not sure if it is an issue with the drive due to it checking out fine with no errors in repair or permissions. Any other ideas?

    Grady Ryan Smith, October 10, 2013 1:57 am | permalink

  • Hm, can’t say I can offer any advice here. I haven’t messed around with Bootcamp in years.

    I’d suggest looking in System Preferences > Startup Disk and seeing if yours is selected. That might at least get you going to OS X automatically.

    Shawn, October 10, 2013 9:39 pm | permalink

  • I have tried almost everything before (frustratingly) calling it a day and getting on the train home. Now that I read your solution I just can’t wait to be back on Monday to tried it out. Same on my Mac Minis, question mark folder and no disk show up when holding the Option key. However, I can see all the data in Recovery Mode and the disks appear alright. Interesting solution anyway, thanks for sharing it.

    Okiharaherbst, May 23, 2014 3:26 pm | permalink

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